Studies in myrsinaceae I. A contribution to the embryology of Maesa dubia wall

Abstract

Maesa dubia (Tribe Maesoideae) of the family Myrsinaceae shows some interesting embryological features. The floral parts arise in acropetal succession. The vascular bundle of each stamen divides in the connective. The tetrasporangiate anthers dehisce by longitudinal slits shedding the pollen at the 2-celled stage. The endothecium and the next layer develop fibrillar thickenings except at the region of dehiscence. The ovules are anatropous, tenuinucellar and bitegmic. The micropyle is organised by both the integuments. While there is usually a single hypodermal archesporium there is a tendency for the differentiation of multiple archesporium. Only one archesporial cell functions and develops into megaspore mother cell. The tetrad of megaspores is usually linear. Some abnormalities in the sequence of degeneration of the three micropylar megaspores are observed. The development of the female gametophyte follows the Polygonum type. A prominent endothelium is differentiated at the dyad stage in the ovule. The chalazal half of the embryo sac forms an aggressive haustorium.